New York Agricultural Experiment Station. U99 



use as an insecticide Paris green or other similar materials that 

 yield more than 3^ per ct. of water-soluble arsenic compounds 

 expressed as arsenious oxide, when treated for 24 hours with 

 distilled water at the rate of 1000 parts of water for one part of 

 Paris green or arsenic-containing materials. 



The water-soluble arsenious oxide varies in the 40 samples 

 of Paris green examined from 0.88 to 2.64 per ct., and averages 

 1.28, which is far below the limit of harm prescribed for use as 

 an insecticide and the limit fixed by law. 



3. Copper in Paris green determined as copper oxide. — The 

 amount of copper expressed as the equivalent of copper oxide, 

 varies in the 40 samples of Paris green examined from 26.53 

 to 31.14 per ct. and averages 29.88 per ct., which is about the 

 same as last year. 



4. Amount of arsenious oxide in combination ivith copper. — The 

 law relating to Paris green in this State was amended in 1901, 

 so as to correct certain defects existing in the original law with 

 reference to the definition of Paris green. The original law 

 required that Paris green should contairi the equivailent of 50 

 per ct. of arsenious oxide. This provision was needlessly low 

 and was also open to the very serious objection that it permit- 

 ted indefinite adulteration by common white arsenic. This 

 defect has been corrected by requiring that Paris green shall 

 contain arsenic in combination tmth copper, equivalent to not less 

 than 50 per ct. of arsenious oxide. In ascertainig the amount 

 of copper in combination with arsenic, it has been assumed 

 that all the copper present was so combined, except when found 

 in excess. While this assumption is not strictly accurate, it 

 answers the purpose, especially when the precaution is taken 

 to examine the Paris green for water-soluble forms of copper- 

 compounds. 



In the 40 samples of Paris green examined the amount of 

 arsenious oxide in combination with copper varied from 49.70 

 to 57.72 per ct. and averaged 55.98 per ct., which is about 6 

 per ct. higher than the minimum required by law. Only one 

 sample fell below the limit and this was only slightly below. 



